1. Field of the Invention
The present invention relates to an optical disk recording apparatus for recording a data signal onto a disk using an optical beam emitted from an optical head, and more particularly to an optical disk recording apparatus capable of switching a recording speed for data recording onto a disk.
2. Description of Related Art
CD-R/RW drives for CD-R (Recordable) and CD-RW(ReWritable) systems of the CD family are well known optical disk recording apparatuses for recording a digital data signal onto a disk using an optical beam emitted from an optical head. In these optical disk recording apparatuses, attempts are being made to achieve higher recording speeds.
At present, the maximum recording speed for CD-R has reached a speed which is 20 or 24 times the normal speed (hereinafter referred to as “20×” or “24×”) and the maximum recording speed for CD-RW has reached 10× speed. In particular, with regard to CD-R for which the maximum recording speed has reached the speed 20× or 24×, a control method of CAV (Constant Angular Velocity) for controlling a rotation speed of a disk at a constant angular velocity or ZCLV (Zone Constant Linear Velocity) in which a disk is divided into a plurality of zones and each zone is controlled at a different constant linear velocity, is typically employed in view of acceleration and deceleration of disk rotation.
Here, materials used for disks onto which data is recorded by such an optical disk recording apparatus differ depending on manufacturer and grade (corresponding to speed), and this further results in variations in recording properties such as sensitivity and frequency characteristics. Furthermore, the recording properties may vary due to manufacturing variations, or may vary in different portions of a single disk due to the non-uniformity of these portions
Therefore, in optical disk recording apparatuses, compensation is made for the recording properties of a disk in accordance with the recording speed so that preferable recording can be performed. Specifically, a data signal is actually recorded onto a disk at a determined recording speed and then read by an optical head, and a HF (high frequency) signal obtained from the optical head is used to detect the recording state of the disk. Then, the emission power (laser power) of the optical head is controlled based on the detected recording state, to thereby compensate for the recording properties of the disk corresponding to the recording speed.
The emission power of the optical head is generally set through detection of a β value (the recording depth) from peak and bottom values of a HF signal read out from the disk. It is also possible to detect a jitter amount contained in the HF signal for determining the emission powers of the optical disk. The setting of emission power is performed as follows. Specifically, when starting a recording operation, test signals are written into a Power Calibration Area (which is provided separately from a program area for use in writing of data signals) of a disk while emission powers are changed stepwise, and the writing results are read by the optical head to obtain a HF signal. The emission power control is performed based on this HF signal.
However, even when the emission power of the optical head is set at an optimal level for disk recording in accordance with the recording speed, the following problems will occur if the disk is not adaptable to the set recording speed or has inferior quality. Namely, in such a case, even if recording is successfully performed, the data signal recorded on the disk cannot be read.
Here, the data signal recorded on the disk cannot be read mainly because a great amount of jitter is contained in the HF signal read from the disk.
Accordingly, by reducing a jitter amount in the HF signal, recording failure caused by the fact that data signals recorded on the disk cannot be read can be significantly decreased.
Because the jitter amount of HF signal cannot be reduced simply by controlling the emission power of the optical head, however, other solutions have been desired.
Further, during disk recording operation, emission power control of the optical head, referred to as Running OPC (Optimum Power Control), may be performed. For Running OPC, it is necessary to detect the recording state of a data signal upon recording the data signal on the disk in the disk recording operation. Conventionally, the recording state of data signal is detected from reflection of an optical beam used for recording (namely, a beam at recording level).
According to the above-described conventional method, however, detection of recording state is not based on actual reading of data signals recorded on the disk. Further, this method does not enable extraction of a jitter component contained in the read HF signal. For these reasons, with this conventional method there are cases wherein the emission power of the optical head cannot be set at the actual optimum recording level. In such cases, recording in accordance with the recording properties of the disk is impossible and recording will fail.
Also, optical disk recording apparatuses have the following problems, when the CAV or ZCLV method is employed so as to increase the recording speed. Specifically, according to these methods, because it is necessary to change data for setting the emission power of the optical head in accordance with the recording speed which changes in accordance with the diameter of the disk, data required for Running OPC cannot be obtained.